Do tougher gun laws lead to ‘dramatically lower rates of gun violence’?

This is Part 2 of two fact checks examining rhetoric on both sides of the gun debate. (Read Part 1 here)

“What we know is that states that have tougher gun laws, that keep criminals from getting guns, that keep those dangerous weapons like AR-15s out of the hands of civilians, have dramatically lower rates of gun violence.”— Sen. Chris Murphy (D-Conn.), remarks during an appearance on CNN’s “State of the Union,” Oct. 8, 2017

In the wake of the mass shooting in Las Vegas that left 58 people dead and hundreds wounded, congressional leaders have reopened the debate over gun-control legislation.

On one side of the debate, politicians argue that not only is the right to bear arms protected by the Second Amendment but also that many of the proposed gun policies aren’t effective. On another side of the debate, members of Congress are calling for policies that they argue could prevent mass shootings and keep guns out the wrong hands.

This is part two of two columns digging into the dueling claims on gun-control policy. On the surface, this seems like a simple case of cutting through the rhetoric to figure out what the facts tell us about gun control. But the fact of the matter is the evidence on both sides of the debate is murky. Let’s take a look.

The Facts

During an appearance on CNN’s “State of the Union” on Oct. 8, Sen. Chris Murphy (D-Conn.) asserted that tough gun laws do work, pointing generally to low rates of gun violence in states with tough laws.

Let’s deal with the AR-15 portion of Murphy’s claim first. To support the senator’s contention that tough gun laws lead to reduced gun violence, Murphy’s spokesperson pointed to several studies that examine the effect of changes in gun laws in several states. None of the studies address bans on assault weapons such as the AR-15, but the effectiveness of an assault weapons ban was widely studied after Congress imposed a nationwide 10-year ban in 1994.

In 2004, Christopher Koper of George Mason University and colleagues released a report analyzing the effect of the ban on gun crimes. The effectiveness of the ban was inconclusive. Gun violence declined nationwide into the 2000s, but the researchers “cannot clearly credit the ban with any of the nation’s recent drop in gun violence.” The researchers estimated that the effects of the ban “may not be fully felt for several years into the future.” And, “should it be renewed, the ban’s effects on gun violence are likely to be small at best and perhaps too small for reliable measurement.” The ban was not renewed.

To be fair, the ban had some limitations. For one, assault weapons were not widely used in gun crimes prior to the ban. And, the ban may not have covered all forms of assault weapons because it did not ban all semiautomatic weapons. Instead, it banned semiautomatic weapons with large capacity magazines and weapons that “appear useful in military and criminal applications but unnecessary in shooting sports or self-defense.”

Murphy cities several studies addressing the connection between gun laws and gun violence. One of the studies from Johns Hopkins evaluates the impact of Missouri’s repeal of a “permit-to-purchase” (PTP) law in 2007. The repeal was associated with a 23 percent increase in annual firearm-related homicides. The researchers concluded that repealing the law “was associated with an additional 55 to 63 murders per year in Missouri between 2008 and 2012 than would have been forecasted had the PTP handgun law not been repealed.”

The study runs into several problems. First, it doesn’t make Murphy’s claim. The study shows that repealing a law led to increased gun violence, not that tougher laws reduced gun violence.

Second, it still focuses on a law change in a single state. In Part 1 of this series, when we evaluated Rep. Steve Scalise’s (R-La.) claim that gun laws don’t work, criminologist Gary Kleck pointed out that using a single state opens the door for cherry-picking the data to fit the agenda.

And third, it is hard to control for all the variables that could have produced the observed changes, said gun-rights advocate John R. Lott Jr.

“We can try to control for income, poverty, law enforcement, demographics, etc., but there are other differences with culture and other factors that we can’t measure very well,” he said.

The Johns Hopkins researchers acknowledge this. Even though they controlled for numerous factors — including poverty, unemployment, incarceration rates, and changes in policing — there were other compounding factors that could have influenced the results.

When the researchers controlled for the effects of Missouri’s “stand your ground” laws that also went into effect in 2007, the estimated effect of the repeal of the PTP law on the homicide rate declined slightly, although it was still statically significant.

Here’s the kicker: The researchers caution that passing PTP laws “may not result in as immediate and large a reduction in firearm homicides as occurred in reverse when Missouri’s law was repealed.” Moreover, they don’t know how their findings could be generalized to other states.

The remainder of the studies cited by Murphy’s spokesperson address suicides and gun-trafficking. Regular readers of The Fact Checker may remember we awarded President Barack Obama Two Pinocchios for making a similar claim in 2015 about gun deaths. Obama’s statements were based on a chart published in the National Journal entitled, “The States With the Most Gun Laws See the Fewest Gun-Related Deaths.”

In the previous column, we crunched the numbers to see what happens when suicides are removed from the total number of gun deaths. And in many cases, the results changed, sometimes dramatically. That’s because most gun deaths, nearly 60 percent, are suicides.

Spokesperson Chris Harris says the Senator has been a long-time advocate of tightening gun laws to reduce suicides, which are a focus of the gun violence prevention movement.

“As years of reporting in the Washington Post shows gun violence goes down in places that have laws that keep guns away from people who pose a danger to themselves or others,” wrote Harris in an email.

There are some gun-control policies that appear to be effective in reducing violence. In October 2016, Kleck co-published a study in Criminal Justice Review addressing the connection between 19 different gun-control laws and violent crime in roughly 1,000 U.S. cities. Kleck found that “gun control laws generally show no evidence of effects on crime rates, possibly because gun levels do not have a net positive effect on violence rates.” But there were a few exceptions. Requiring a license to possess a gun and bans on gun purchases by alcoholics appeared to reduce the homicide and robbery rate.

The Pinocchio Test

The evidence to support Murphy’s claim is thin, at best. A 10-year ban on assault weapons such as AR-15s didn’t do much to reduce gun violence. Many of the studies that show gun control reduces gun deaths include suicides, which distorts the results. And single-state studies may show improvements in gun violence, but the results can’t be readily generalized to other states. (The Fact Checker once documented how proposed gun laws would not have prevented any mass shootings that took place between 2012 and 2015.)

After each mass shooting, politicians argue over gun-control policy, with one side focused on how to prevent the next shooting, and the other asserting that gun ownership is a constitutional right and that most gun laws don’t work. The best evidence available doesn’t lend much support for either side of the debate. Nevertheless, politicians can only work with the information they have available. And the reality is, as Kleck points out: “We make policy on the basis of incomplete and imperfect information.”

The best data available show gun permits and restricted sales slightly reduce homicides and robberies. Still, there is no evidence that tough laws “dramatically reduce” gun violence as Murphy claims. He exaggerates the little evidence that lends just a hint of support for his side of the gun debate. For this we award him Three Pinocchios — yet again.

“What we know is that states that have tougher gun laws, that keep criminals from getting guns, that keep those dangerous weapons like AR-15s out of the hands of civilians, have dramatically lower rates of gun violence.”